Nothing a dab of 5200 wouldn't take care of. what do you mean by serviceability
Since the bolt would not be captive, every time I needed to pull the motor mounts I would likely have to chip off the 5200 and clean it up just to get an allen on it to tighten the mounts to the hull, otherwise it will just spin.
Just a different order of operation to learn, nothing that is a deal breaker. Would add 30 minutes to a motor mount install down the line.
The bolts through the hull seems like a super strong solution, I would probably never lose the mounts.
I still have not discounted the embedded aluminum plate an an option. While a lot more work it seems like a more traditional solution.
Additionally I have an idea kicking around that is a hybrid of the two ideas. Bolts countersunk into the the glass from the bottom and threaded into the epoxied plate from underneath with cabosil and glass covering the bottom of the bolt heads. Cover the top in eglass and tap the mounts as originally planned for motor mounts. the plate would never come out and the motor mounts would take stock yamaha hardware. It would take even longer to do but I am a glutton for punishment so I am considering it.
Decisions decision.